News about our knowledge of the brain and behavior
from Anthony Risser, Ph.D.

Tuesday, August 14, 2007

Dementia and the Sniff Magnitude Test

From today's New York Times:

Sniff Test May Signal Disorders’ Early Stages By ELIZABETH SVOBODAPublished: August 14, 2007

[snip]

The Sniff Magnitude Test, developed with the aid of a $1.3 million grant from the National Institutes of Health, consists of a nasal tube called a cannula attached to a plastic container about the size and shape of a coffee thermos. Chemical vapors inside the canister are released through the tube, exposing subjects to a series of smells, some more objectionable than others.

“People describe some of the smells as skunky or sewerlike,” said Jason Bailie, a University of Cincinnati graduate student working on the test. “There’s also one that smells like banana.”

As patients take whiffs of each new fragrance, sensors in the thermos unit measure the negative pressure the inhalations produce. The size and intensity of these sniffs turn out to be important gauges of olfactory ability. After detecting a strong or disagreeable odor, people with a normal sense of smell take very small sniffs to avoid smelling it. Subjects with an impaired sense of smell, on the other hand, continue taking deep whiffs, because the scent does not register in their brains.

[snip]

The Cincinnati team’s efforts have piqued the interest of other researchers, including Dr. Doty and Alan Hirsch of the Smell and Taste Research and Treatment Foundation, who is using the Sniff test in his clinical practice. “They’ve chosen some very good odors that stimulate the olfactory system effectively,” Dr. Doty said. “This is a very novel approach — it just needs to be tested more broadly.”

Still, Dr. Doty added, the Sniff Magnitude Test may not be the ideal way to assess every patient with cognitive deficits. “Very early in life, we make a connection between an odor and its source,” he said. “We give it a name. If the connection between the name of an odor and the odor itself is what’s breaking down in an Alzheimer’s patient, this test might not be as helpful,” because it does not tell evaluators how a patient identifies and categorizes smells. The Sniff Magnitude Test is likely to raise red flags only if an impending cognitive disorder directly affects a patient’s olfactory abilities.